Questions tagged [biochemistry]
The study of chemistry within the scope of biology: the compounds that occur and the reactions involving them in living organisms.
2,001
questions
118
votes
3
answers
120k
views
Why is thymine rather than uracil used in DNA?
What is the advantage gained by the substitution of thymine for uracil in DNA? I have read previously that it is due to thymine being "better protected" and therefore more suited to the storage role ...
- 13.5k
84
votes
4
answers
136k
views
Death because of distilled water consumption
One of my friends said that I would die if I drank distilled water (we were using it in a chemistry experiment) I gave it a go and surprisingly did not die.
I did a bit of Googling and found this
...
- 1,169
84
votes
2
answers
31k
views
Why is the heart not in the middle of the body?
All mammals that I can think of have a high degree of bilateral symmetry (In fact, almost every animal I can think of is like this).
So why is the human heart not exactly in the middle of the body? ...
- 1,421
81
votes
3
answers
21k
views
Why 20 amino acids instead of 64?
This question got me thinking about amino acids and the ambiguity in the genetic code. With 4 nucleotides in RNA and 3 per codon, there are 64 codons. However, these 64 codons only code for 20 amino ...
- 5,721
59
votes
10
answers
18k
views
Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)
Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
- 723
54
votes
5
answers
3k
views
Human perception of time depending on age
From what I can tell and what thus far all people with whom I discussed this subject confirmed is that time appears to "accelerate" as we age.
Digging a little, most explanations I found basically ...
- 883
53
votes
3
answers
3k
views
Can scientists create totally synthetic life?
This particular question has been of a great deal of interest to me, especially since it dives at the heart of abiogenesis.
- 2,146
50
votes
2
answers
10k
views
Why does cutting onions cause tears?
Why does cutting onions cause tears? From a couple of sites, I found that it is because of sulfuric acid produced by onions. But I could not find more details. What is the biochemical pathway by ...
- 829
45
votes
4
answers
10k
views
Why are bruises not lethal?
Given the following:
bruises are caused by minor trauma which breaks blood vessels beneath the skin, causing bleeding
the mechanism by which bleeding stops is clotting
blood clots inside the body ...
- 1,211
41
votes
5
answers
15k
views
What does the human body use oxygen for besides the final electron acceptor in the electron transport chain?
My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. ...
- 3,673
40
votes
2
answers
12k
views
Why do some vegetables taste bitter?
Bitter gourd, cucumber, etc. are bitter to taste. Which chemical causes bitterness in them?
I found these when I searched online: this says that it is because of calcium, while this and this talk ...
- 3,277
37
votes
3
answers
5k
views
What does it mean to "write an image and GIF into the DNA of bacteria"?
BBC News recently published an article saying that:
An image and short film has been encoded in DNA, using the units of inheritance as a medium for storing information ...
The team sequenced the ...
- 373
35
votes
3
answers
61k
views
Why is ATP the preferred choice for energy carriers?
Why is ATP the most prevalent form of chemical energy storage and utilization in most cells?
- 1,517
35
votes
1
answer
4k
views
Ripening bananas artificially: What is the biological theory behind?
I am a resident of the tropical island of Sri Lanka, and we have a strange traditional method to ripen our banana harvest quickly.
What we do is this: We dig a pit in earth that is enough to put the ...
- 455
34
votes
1
answer
3k
views
Why do animal cells "mistake" rubidium ions for potassium ions?
So, I was browsing the Wikipedia article for rubidium, and came across this interesting tidbit:
Rubidium is not a known nutrient for any living organisms. However, rubidium ions have the same charge ...
- 459
33
votes
5
answers
8k
views
Why isn't Fluorine, or Neon, the final electron acceptor in cellular respiration?
I'm a Chemistry student learning about periodic trends. I know that in (many organisms') cellular respiration, oxygen serves as the final electron acceptor due to its high electronegativity.
However, ...
- 439
32
votes
3
answers
11k
views
Can plants suffer from CO2 poisoning?
Is there a point where too much CO2 is bad for a plant? Basically when there is too much CO2 in the air can a plant get sick?
Since plants photosynthesize and need CO2 to generate glucose and store ...
- 323
29
votes
1
answer
3k
views
Killing enveloped viruses with soap
Unlike non-enveloped viruses, enveloped viruses can be killed with soap, alcohol, etc. Why?
Why does just having an envelope make it susceptible to soap and alcohol?
- 415
29
votes
3
answers
1k
views
How, on a physical level, does ATP confer energy?
When ATP is used as the energy currency to make, say, reaction X + Y → Z happen, is what happens on a physical level down at the molecular scale that during the reaction
ATP + H2O → ADP + Pi &...
- 1,963
28
votes
3
answers
179k
views
NADH vs. NADPH: Where is each one used and why that instead of the other?
I know NADH is used in cellular respiration and NADPH is used in photosynthesis. What difference does the phosphate group make that the same one isn't or can't be used for both? Is there a greater ...
- 3,673
28
votes
4
answers
10k
views
Where does the 'C' in exhaled CO₂ mostly come from?
When a human being exhales CO₂, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
- 1,963
27
votes
7
answers
16k
views
Why are there exactly four nucleobases in DNA?
Does someone know why DNA is composed of four nucleobases? In particular, is there an explanation for the number? Why four and not two, or eight?
- 373
26
votes
3
answers
4k
views
Does any molecule other than DNA have a double-helical structure?
DNA is known to have a double-helical structure. Do any other molecules have this structure?
- 363
26
votes
1
answer
4k
views
Why do mints make your mouth feel cold?
Why do mints make your mouth feel cold? And specifically, why does your mouth feel so cold if you eat a few mints and then drink a glass of cold water afterwards?
- 2,711
26
votes
2
answers
2k
views
What's the mechanism for being mentally tired?
I notice that after long tests, or long periods of critical thinking, my body and mind feel noticeably tired. Why does this happen? Are the neurons in my head not firing as quickly, or is there just a ...
- 323
25
votes
4
answers
164k
views
What is a coupled reaction and why do cells couple reactions?
I was wondering what exactly a coupled reaction is and why cells couple them. I read the wikipedia article as well as several others, such as life.illinois.edu but I still don't get it. Could ...
25
votes
2
answers
19k
views
Do all proteins start with methionine?
Start codon AUG also codes for methionine and without start codon translation does not happen. And even the ambiguous codon GUG codes for methionine when it is first. So does this mean that all ...
- 759
25
votes
1
answer
2k
views
ATP cost for gene expression
How would you estimate the number of ATPs required to transcribe, export and translate a single eukariotic protein?
- 3,864
25
votes
3
answers
22k
views
Why is glucose our primary source of energy?
Is there any evolutionary reason for glucose being the "main" molecule used as a source of energy, beginning with glycolysis and subsequently cellular respiration (after being converted to two ...
- 6,705
24
votes
3
answers
539
views
How crowded is the bacterial cell?
I was wondering what is the protein concentration in an E. coli cell. When studying enzyme kinetics and activity in vitro, I would argue that the substrate and enzyme concentrations resemble those in ...
- 6,925
23
votes
2
answers
13k
views
Is it known how the first viruses formed?
The oldest known virus is known to have infected prehistoric insects 300 million years ago. A virus is basically a parasitic strand if DNA or RNA encapsulated in a protein coat. It enters cells by "...
- 395
23
votes
2
answers
9k
views
What is the mechanism behind "acquired" alcohol tolerance?
I can understand natural variation in alcohol dehydrogenase (ADH) in a population leading to variation in rate of inebriation (after controlling for other variables -- e.g., mass, food consumption, ...
- 12.2k
23
votes
1
answer
792
views
Can a human be made with ovum but without sperm?
This article says that scientists were successful in making a mouse using only a sperm and no egg (ovum). The article also states that this procedure could be applicable to humans.
However, I want to ...
- 3,277
22
votes
3
answers
4k
views
Why does hair turn grey or white, and why does it happen later for some?
The question is pretty simple: what is happening molecularly when hair turns grey or white? I would imagine that it is due to the lack of a particular compound. I'm also interested in why some people'...
- 6,705
22
votes
1
answer
483
views
Evolutionary origin and exogenous cues of ~28 day infradian rhythm?
The most obvious example of an approximately monthly biological cycle is the human menstrual cycle. My questions are the following:
Is it known when and where this cycle or one like it arose?
What ...
- 956
21
votes
3
answers
2k
views
How is RNAse contamination in RNA based experiments prevented?
Does anyone have any suggestions to prevent RNAse contamination when working with RNA?
I tend to have issues with degradation regardless of whether I use DEPC treated / RNAse free water and filtered ...
- 2,125
21
votes
2
answers
2k
views
What inactivates pepsin in infants?
In infants, rennin helps in digestion of milk. Pepsin is also present in their stomach.
Why do infants need rennin for milk digestion, at the first place? Why does pepsin not act on the milk ...
- 3,277
21
votes
1
answer
1k
views
Can siRNA induce DNA methylation in mammalian cells?
Some years ago Hiroaki Kawasaki and Kazunari Taira published an article called "Induction of DNA methylation and gene silencing by short interfering RNAs in human cells" in Nature:
In plants, ...
- 9,174
21
votes
1
answer
1k
views
Why do we feel tired if we sleep excessively?
When we eat, finally we feel full. I know which mechanism causes the sensation of being full. But when we sleep excessively we often still want more sleep. Why does this happen? Is there a mechanism ...
- 2,264
20
votes
2
answers
16k
views
How does a plant grow before photosynthesis is possible?
During photosynthesis, a plant translates CO2, water and light into O2. I assume the carbon C is further used for the growing process. I wonder how the plant grows before the time where photosynthesis ...
- 595
19
votes
3
answers
3k
views
Is atmospheric nitrogen chemically necessary for life?
It is my (very basic) understanding that neither plants nor animals utilize the nitrogen in the atmosphere. Humans do not make use of atmospheric nitrogen through respiration and plants do not ...
- 359
19
votes
3
answers
59k
views
Why can't the brain and red blood cells use fuels other than glucose?
The question is rather straight forward: I have always been curious as to why, but cannot find an explanation online.
I can imagine that the mechanism is different for each, but why does brain tissue ...
- 6,705
19
votes
1
answer
3k
views
Why are sushi proteins called "sushi"? What are the origins of this name?
Does anybody know why complement control proteins (also short consensus repeats) are called "sushi" proteins? Is there any special reason for their name?
- 193
19
votes
1
answer
4k
views
Why do humans require vitamin B12 supplementation while herbivores do not?
This question came about from reading the comments of this (very unclear) question, which the author did not properly clarify.
Vegans are often recommended to take vitamin B12 supplements, as the ...
- 9,432
18
votes
4
answers
9k
views
Why don't antiseptic agents kill 100% germs?
I've seen innumerable antiseptic, mouthwash, handwash advertisements that claim to be able to eliminate as much as 99.9% of all germs over a surface...but why not the remaining 0.1% (i.e- why can't ...
- 1,569
18
votes
1
answer
3k
views
What is the most condensed form of (stored) energy used in biology?
When considering how organisms store energy for later use, I was wondering what substance known in Biology is best for compacting the most energy in the smallest space(volume-wise).
With my (limited) ...
- 505
18
votes
1
answer
4k
views
How do ants follow each other?
I was observing ants in my house.They all were going in a straight line and also some of the ants were coming back through the the same line.
I took some water and rubbed the line with my finger, ...
- 3,277
18
votes
4
answers
23k
views
Why is the brain dependent on glucose?
The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
- 5,675
18
votes
1
answer
554
views
The human brain in numbers I: neurons
Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human ...
18
votes
2
answers
5k
views
Why do specifically bananas go brown quicker in the fridge?
Perhaps the title should be: Why don't all fruits containing phenol residues go brown quickly when left in the fridge?
Bananas go brown over time because of the oxidation of phenol residues.
...
- 11.3k